Vyper45,
Probably not what you want to hear, but ...
The M1S90 relies on recoil to properly cycle. Any method of recoil reduction can have an effect on proper cycling. Even adding weight (e.g. SideSaddle) can cause improper cycling of light loads.
If all you shoot is full power buck/slug loads - no problem.
However, if you ever shoot Dove loads, expect type 2 (failure to eject) function failures if you have altered the gun to reduce recoil.
Yes, even a recoil pad can have this effect. Even not "getting into the gun" enough can cause this type of malfunction with light loads.
HTH